52 J. A. EWING AND J. G. MACGREGOR ON THE 
will be seen that the line thus obtained is at first slightly curvilinear, curving 
upwards, but afterwards becomes as nearly as possible straight. In other 
words, the amount of expansion is not proportional to the quantity of salt 
dissolved in the case of the weaker solutions, but the ratio increases as the 
solutions become stronger, till it is sensibly constant. 
If the expansion had been due to the water of crystallisation, and the 
anhydrous part of the salt had dissolved in the total water present without 
further increase of volume, the line would have been straight, since the amount 
of expansion would be directly as the amount of salt dissolved. The dotted 
line A shows the volumes which would have been obtained if this had been 
the case. The actual volumes of the strong solutions are much greater than 
such a hypothesis would allow them to be; but it is a singular fact that the 
experimental curve passes at first below this straight line, and then crosses and 
rises considerably above it, or, the expansion by the solution of this salt in 
water is less than is accounted for by the water of crystallisation when a small 
quantity of salt is dissolved, but greater when the quantity of salt dissolved is 
great. Owing to the proximity of the two lines, it is difficult to show this 
graphically, but the following table will make it obvious :— 



Ratio of salt to | Actual volume of |Caleulated volume}! Ratio of salt to | Actual volume of |Calculated volume 
water. solution. due to 7H,0. water. solution. due to 7H,0. 
1 to 40 1:0108 10110 1 to 7 10622 10627 
Les s80 10144 10146 gpm es 1:0893 1:0878 
1 ,, 20 1:0216 1-0220 aes 171512 11464 
Le. 10 1:0436 1:0439 &e. &e, &e. 
This result would seem to show that the water of crystallisation is not separated 
from a salt when it is dissolved in water. 
The line B shows what the volumes would have been had the salt simply 
been introduced into the water without being dissolved. It is calculated by 
taking as the density of crystallised sulphate 1:931 (MILLER’s Chemistry). 
SunrHate or Copper (Pure). 






I. Sie. II. 4 TIE if alse III. 
Ratio of CuSO,+ ensity — weight Ratio of volume || Ratio of CuSO,+ Density — weight Ratio of volume 
5H,0 to water oe Oss of solution to 5H,0 to water | ane OY of solution to 
in solution. need * | volume of water. in solution. ea tee * | volume of water. 
1 to 40 1:0167 1:0082 1 to 5 171174 1:0739 
Lo, BO) 1:0216 10115 Ll ee 1°1432 1:0934 
i, BO 1:0318 1:0176 bere as} 1:1823 ea ien 
ih 5, LO) —-1°0622 1:0356 1 ,, 25917 
1°2051 11494 
i pd a7 1:0858 1:0526 Saturated 



